Ventricular cuff

ABSTRACT

An implantable system includes a ventricular assist device and a cuff for attachment to a heart. The ventricular assist device includes an inlet cannula. The cuff defines an opening for insertion of the inlet cannula into the opening. The cuff includes an annular fastening member and an attachment member. The annular fastening member is configured to be sutured to heart tissue. The attachment member includes flexible extensions. Each of the flexible extensions is configured to interface with the inlet cannula during insertion of the inlet cannula into the opening so as to cause the flexible extension to flex outward to accommodate passing of the inlet cannula along the opening. Each of the flexible extensions is configured to interface with the inlet cannula to impede extraction of the inlet cannula from the opening.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No. 16/049,061 filed Jul. 30, 2018 (Allowed); which is a Continuation of U.S. application Ser. No. 15/667,321 filed Aug. 2, 2017 (now U.S. Pat. No. 10,111,993); which is a Divisional of U.S. application Ser. No. 14/817,819 filed Aug. 4, 2015 (now U.S. Pat. No. 9,750,858); which is a Divisional of U.S. application Ser. No. 13/410,670 filed Mar. 2, 2012 (now U.S. Pat. No. 9,144,637); which claims the benefit of U.S. Provisional Appln No. 61/448,434 filed Mar. 2, 2011; the full disclosures which are incorporated herein by reference in their entirety for all purposes.

TECHNICAL FIELD

This disclosure relates to ventricular cuffs.

BACKGROUND

Heart assist devices or pumps can be inserted in the circulatory system to pump blood from either ventricle or atrium of a heart to the vasculature. A pump supplementing a ventricle is known as a ventricular assist device, or VAD. A VAD is useful when the ventricle alone is incapable of providing adequate blood flow.

BRIEF SUMMARY

In a general aspect, a cuff for attachment to a heart defines an opening to admit a cannula of a heart pump. A coupling mechanism couples the cuff about the cannula, and a locking mechanism secures the position of the cuff set by the coupling mechanism.

In another general aspect, an implantable system includes a cuff, a surface defining channels, and a clip having arms that extend into the channels. The arms travel along the channels during movement of the clip between an unlocked position of the clip and a locked position of the clip. The clip permits the cuff to be coupled about a cannula when the clip is in the unlocked position, and the clip is configured to secure the cuff relative to the cannula when the clip is in the locked position.

Implementations can include one or more of the following features. For example, the implantable system includes a cover, and the clip is captured between the cover and the surface. The cannula has a longitudinal axis, and the clip moves between the unlocked position and the locked position in a plane perpendicular to the longitudinal axis. The cover and the surface define a slot, and the clip travels along a linear direction through the slot to enter the locked position. The channels define detents, and when the cuff is not coupled to the cannula, movement of the clip from the unlocked position toward the locked position engages the arms into the detents to impede the clip from entering the locked position. Each of the arms can engage a detent independent of whether another arm engages a detent, and engagement of any of the arms with a detent impedes the clip from entering the locked position. When the clip moves toward the locked position and the cuff is coupled about the cannula, the arms engage the cuff to avoid the detents. The arms include teeth configured to limit rotation of the cuff about the cannula when the clip is in the locked position. A sealing ring is disposed about the cannula, and the sealing ring is engageable to an inner surface of the cuff to couple the cuff to the cannula. The clip includes a visual indicator disposed such that the visual indicator is exposed when the clip is not in the locked position and the visual indicator is obscured when the clip is in the locked position. The clip includes a latch that impedes the clip from exiting the locked position.

In another general aspect, an implant includes a cuff defining an opening configured to receive a cannula coupled to a heart pump and a coupling mechanism having a first position and a second position. The cuff is uncoupled from the cannula in the first position and the coupling mechanism couples the cuff to the cannula in the second position. The implant includes a locking mechanism configured to secure the coupling mechanism in the second position, and the locking mechanism is configured to be moved to a locked position after the coupling mechanism is in the second position.

Implementations can include one or more of the following features. For example, a first action positions the coupling mechanism in the second position, and a second action activates the locking mechanism to secure the coupling mechanism in the second position, and the second action occurs subsequent to and separate from the first action. The cannula includes a flange and a circumferential ridge, and the coupling mechanism is configured to capture the cuff about the cannula between the flange and the circumferential ridge. The cannula includes (i) an attachment portion between the flange and the circumferential ridge and (ii) an inflow portion, and the attachment portion has an outer diameter greater than an outer diameter of the inflow portion. The cuff includes an inner portion, an outer portion, and a member each disposed concentrically about the opening, the member being disposed between the inner portion and the outer portion, and the outer portion extending in a direction generally perpendicular to the member. The coupling mechanism includes a clamp coupled to the cuff and disposed about the opening.

Implementations can include one or more of the following features. The clamp has a first end and a second end, the clamp configured such that bringing the first end near the second end opens the clamp and moving the two ends apart closes the clamp. The locking mechanism includes a cam that defines a channel, the cam being coupled to the first end of the clamp and being configured to rotate about the first end, the second end of the clamp being disposed in the channel and being configured to travel within the channel. The channel includes a curved portion, the curved portion being configured to limit the motion of the second end of the clamp in the channel when the clamp is closed. The coupling mechanism includes an attachment member coupled about the opening of the cuff, the attachment member having one or more flanged portions that extend outward from the opening, and the locking mechanism includes a clip configured engage the flanged portions to limit movement of the cuff relative to the cannula. The clip is configured to enter a slot in the pump to secure the cuff to the pump. The attachment member includes one or more extensions each including a contact portion that extends toward the opening, the cannula includes a tapered circumferential ridge, and the second position of the coupling mechanism, the contact portions are disposed between the pump and the circumferential ridge along the length of the cannula.

In another general aspect, a cuff for attachment to a heart includes a member defining an opening, a seal coupled to the member and disposed about the opening, and a clamp coupled to the seal and disposed about the opening. The clamp has a first end and a second end, and the clamp is configured such that (i) bringing the first end near the second end opens the clamp and (ii) moving the first end and the second end apart closes the clamp.

Implementations can include one or more of the following features. For example, a cam defining a channel, the cam being coupled to the first end of the clamp and being configured to rotate about the first end, the second end of the clamp being disposed in the channel and being configured to travel within the channel.

In another general aspect, a cuff for attachment to a heart includes a member defining an opening, a linking member coupled to the member and disposed about the opening, and an attachment member coupled to the linking member and disposed about the opening. The linking member extends about an outer surface of the attachment member. The attachment member is configured to attach the cuff to a cannula disposed through the opening. The attachment member has at least one flanged portion extending outward from the opening in a plane generally perpendicular to a circular portion of the attachment member.

Implementations can include one or more of the following features. For example, the linking member is molded over a portion of the attachment member, and the attachment member is coupled to the member through the linking member. The attachment member includes at least one extension disposed generally perpendicular to the member, the extension having a tapered portion disposed on a surface of the extension facing toward the opening. The attachment member defines circumferential groove configured to admit a sealing ring. The linking member includes an elastomer. The linking member is configured to form a seal.

In another general aspect, a method of attaching a ventricular assist device to a patient, includes: attaching a cuff to a heart, the cuff defining an opening; removing tissue of the heart through the opening of the cuff; inserting a cannula through the opening of the cuff; engaging a coupling mechanism to set a position of the cuff relative to the cannula; and engaging a locking mechanism to secure the position of the cuff relative to the cannula.

Implementations can include one or more of the following features. For example, selecting a location near the apex of the heart to attach the cuff. Engaging a cardiac bypass system so that blood is not circulating through the heart. Engaging the coupling mechanism includes inserting a tapered portion of the cannula into the cuff so that one or more extensions of the cuff engage a groove defined adjacent to the tapered portion. Engaging the locking mechanism includes inserting a clip that engages the cuff and a pump coupled to the cannula. Engaging the coupling mechanism includes closing a clamp coupled to the cuff so that the clamp engages a groove defined in the cannula. Engaging the locking mechanism includes capturing an end of a clamp to secure the clamp in a locked position. Engaging the coupling mechanism to set a position of the cuff relative to the cannula includes positioning the cuff such that an inner surface of the cuff engages a sealing ring disposed about the cannula and a bottom surface of the cuff engages a surface of the cannula or a surface of a pump that is coupled to the cannula. Engaging the locking mechanism includes moving a clip in a plane perpendicular to the cannula. Engaging the locking mechanism includes moving a clip into a locked position about the cuff, the clip limiting travel of the cannula out of the cuff. Engaging the locking mechanism includes engaging a latch that secures the clip in the locked position.

In another general aspect, a system includes a cuff having an annular member defining an opening and an attachment member disposed about the opening. The attachment member includes a flanged portion oriented generally parallel to the annular member, and the flanged portion extends outward from the opening. A clip is configured to be coupled about the attachment member between the annular member and the flanged portion.

Implementations can include one or more of the following features. For example, the system includes a pump assembly that includes a cannula, and the clip is configured to travel relative to the pump assembly from an unlocked position to a locked position in which the clip secures the cuff about the cannula. The clip is configured to travel along a substantially linear path from the unlocked position to the locked position. When the cuff is coupled to the pump assembly and the clip is in the locked position, the clip impedes rotation of the cuff about the cannula. The cuff includes ridges disposed on the attachment member, and the clip is configured to engage the ridges to impede rotation of the cuff. The clip is configured to engage the pump assembly such that the travel of clip to the locked position is impeded when the cuff is improperly seated about the cannula. The clip is configured to engage the pump assembly such that travel of clip to the locked position is impeded when the cuff is not coupled to the pump assembly. The system includes a visual indicator that is visible when the clip is not in the locked position and is obscured when the clip is in the locked position. When the clip is in the locked position, engagement of the clip and the pump assembly impedes travel of the clip out of the locked position. The clip has arms that are configured to extend about the cuff in the locked position, the arms being configured such that any of the arms can engage the pump assembly to impede travel of the clip into the locking position.

In another general aspect, a system includes a cuff having a member defining an opening and an attachment member disposed about the opening. The attachment member includes (i) a clamp having a first end and a second end, and (ii) a cam defining a channel. The cam is coupled to the first end of the clamp and is configured to rotate about the first end. The second end of the clamp is disposed in the channel and is configured to travel within the channel.

The features described can be used in any appropriate combination and subcombination, including combinations across multiple aspects described above. Features described with respect to one aspect can additionally or alternatively be included in implementations of any of the other aspects. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a pump installed at a heart.

FIG. 2A is a perspective view of a ventricular cuff.

FIG. 2B is a side view of a cannula for coupling to the ventricular cuff.

FIG. 3 is an exploded view of the ventricular cuff.

FIG. 4A is a perspective view of a tube from which a seal member of the ventricular cuff can be fabricated.

FIG. 4B is a perspective view of a seal member of the ventricular cuff.

FIG. 5A is a perspective view of a cam of the ventricular cuff.

FIGS. 5B to 5E are respectively top, bottom, lateral side, and opposite lateral side views of the ventricular cuff.

FIG. 6 is a side cross-sectional view of the ventricular cuff coupled to the cannula across line 6-6 of FIG. 8D.

FIGS. 7A to 7D are top views illustrating the closing of a clamp of the ventricular cuff.

FIGS. 8A to 8D and 9A to 9C are perspective views illustrating the coupling of the ventricular cuff to the pump.

FIGS. 10A to 10D are perspective views illustrating a process for implanting the ventricular cuff and the pump.

FIG. 11A is a perspective view of a ventricular cuff.

FIG. 11B is a side view of a cannula for coupling to the ventricular cuff of FIG. 11A.

FIG. 12A is a perspective view of an attachment member of the ventricular cuff of FIG. 11A.

FIG. 12B is a side cutaway view of an extension of the attachment member.

FIG. 13A is a perspective view illustrating the top of a clip.

FIG. 13B is a perspective view illustrating the bottom of the clip.

FIG. 13C is a side view of a post of the clip.

FIGS. 14A to 14C are perspective views illustrating the engagement of the clip with a pump.

FIGS. 15A to 15C are perspective views illustrating the coupling of the pump of FIG. 14A to the ventricular cuff of FIG. 11A using the clip.

FIG. 16 is a side cross-sectional view of the ventricular cuff of FIG. 11A coupled to the cannula of FIG. 11B across line 16-16 of FIG. 15C.

FIG. 17A is a perspective view of a ventricular cuff.

FIG. 17B is a side view of a cannula for coupling to the ventricular cuff of FIG. 17A.

FIG. 18A is a perspective view of an attachment member of the ventricular cuff of FIG. 17A.

FIG. 18B is a cross-sectional view of a portion of the ventricular cuff of FIG. 17A.

FIGS. 19A and 19B are cross-sectional views illustrating the engagement of the ventricular cuff of FIG. 17A with the cannula of FIG. 17B.

FIG. 20 is a side cross-sectional view of the ventricular cuff of FIG. 17A coupled to the cannula of FIG. 17B and secured to the pump of FIG. 14A using the clip.

FIG. 21 is a perspective view of a pump, a cannula, and a ventricular cuff.

FIG. 22A is a perspective view of the cuff of FIG. 21.

FIG. 22B is a side view of the ventricular cuff of FIG. 21.

FIG. 22C is a perspective view of an attachment member of the ventricular cuff of FIG. 21.

FIG. 22D is a side cutaway view of the ventricular cuff of FIG. 21.

FIGS. 23A and 23B are side cutaway views of the cannula and ventricular cuff of FIG. 21.

FIGS. 24A and 24B are cross-sectional view of sealing rings.

FIG. 25A is a perspective view of the pump of FIG. 21.

FIG. 25B is an exploded view of the pump of FIG. 21.

FIG. 26A is a top perspective view of a clip that cooperates with the pump and the ventricular cuff of FIG. 21.

FIG. 26B is a bottom perspective view of the clip of FIG. 26A.

FIG. 26C is a side view of an end portion of an arm of the clip of FIG. 26A.

FIG. 26D is a side cross-sectional view of a tooth of the clip of FIG. 26A.

FIG. 27 is a perspective view of a surface of the pump of FIG. 21.

FIGS. 28A to 28C are perspective views illustrating different motions of the clip of FIG. 26A relative to the pump of FIG. 21.

FIGS. 29A to 29C are bottom views of different positions of the clip of FIG. 26A relative to the pump of FIG. 21.

FIGS. 30A to 30C are top perspective views of different positions of the clip of FIG. 26A relative to the pump of FIG. 21.

FIG. 31 is a side cutaway view of the pump, the cannula, and the ventricular cuff of FIG. 21.

DETAILED DESCRIPTION

Referring to FIG. 1, a ventricular assist system 10 for treating, for example, a patient with a weakened left ventricle, includes a blood pump 12 that receives blood from a patient's heart 14. The pump 12 is coupled to a cuff 20, which in turn is attached to the heart 14. The cuff 20 is attached to the heart by, for example, sutures that attach a portion of the cuff 20 to the apex of the left ventricle of the heart 14. The pump 12 receives blood from the heart through an inflow cannula 50 (FIG. 2B) of the pump 12 disposed through an opening in the cuff 20.

Referring to FIGS. 2A and 2B, the cuff 20 defines an opening 30 that admits the inflow cannula 50. The cuff 20 includes a coupling mechanism, for example, a clamp 26 that couples the cuff 20 to the cannula 50. The cuff 20 also includes a locking mechanism in the form of a cam 28 that secures the clamp 26 in a closed position. The locking mechanism, by maintaining the position of the coupling mechanism, limits the possibility of the cuff 20 accidentally becoming uncoupled from the cannula 50. The locking mechanism can secure the cuff 20 to the cannula 50 such that, for example, removal of the cuff 20 from the cannula 50 requires more than one action, or the cannula 50 is no longer free to rotate or translate with respect to the cannula 50 without significant outside influence, such as by a clinician.

Referring to FIG. 3, the cuff 20 is illustrated in a view illustrating individual disassembled parts, including a fastening member 22, a linking member 24, the clamp 26, and the cam 28. The components illustrated can be preassembled and delivered to a clinician as a single unit. The fastening member 22 is generally ring-shaped and includes a contact surface 23 to contact heart tissue. The fastening member 22 is composed of a material through which sutures can be placed, for example a fabric such as polytetrafluoroethylene (PTFE) felt. In an implanted state, sutures or staples bind the fastening member 22 to heart tissue to couple the cuff 20 to the heart 14. In one embodiment, the fastening member 22 and the linking member 24 are pre-assembled together as one unit.

Referring to FIGS. 4A and 4B, the linking member 24 can be fabricated by reshaping a tube 25 formed of, for example, an elastomer such as silicone. The linking member 24 is formed, for example, by folding an upper portion 32 of the tube 25 and a lower portion 33 of the tube 25 about an outer circumference 31 of the tube 25. The resulting linking member 24 defines a circumferential groove 34 between generally parallel ring-shaped portions 35, 36. The linking member 24 also includes a circumferential inner surface 40 that forms a seal with the cannula 50.

The linking member 24 can also be fabricated to include ring-shaped reinforcement members 37, 38 (FIG. 6) that includes, for example, a mesh material or a knitted fabric formed of a material such as polyester. A knitted fabric or mesh material is embedded into a silicone sheet. The silicone sheet is die-cut into ring-shaped portions 35, 36 that respectively include the ring-shaped reinforcement members 38, 37. The ring-shaped portions 35, 36 are then placed in a silicone mold and overmolded with additional silicone. The molded silicone binds the ring-shaped portions 35, 36 together and creates a flexible connection between the ring-shaped portions 35, 36, which include the reinforcement members 38, 37.

Referring to FIG. 2A and FIG. 3, the clamp 26 includes a circular portion 70 formed of a resilient material, such as metal wire. For example, the circular portion 70 can be formed of stainless steel or a cobalt chromium alloy, each of which can provide implantability, long term stability, and resiliency. In the assembled cuff 20, the circular portion 70 is disposed in the circumferential groove 34 of the linking member 24. The linking member 24 is thus couples the clamp 26 to the fastening member 22. Sutures 42 pass through the fastening member 22 and the ring-shaped portions 35, 36 of the linking member 24, capturing the circular portion 70 in the linking member 24 and coupling the linking member 24 to the fastening member 22. The reinforcement members 37, 38 limit tearing of the linking member 24 by the sutures 42. In addition to, or instead of, sutures 42, the linking member 24 can be coupled to the fastening member 22 by an adhesive or by overmolding the linking member 24 over a portion of the fastening member 22.

The clamp 26 has a relaxed position toward which it wants to return after a load is applied to open or close the clamp 26. The circular portion 70 is expanded by moving the arms 72, 74 closer together. The circular portion 70 is contracted by increasing the distance between the arms 72, 74. Expansion of the circular portion 70 beyond the relaxed position loads the circular portion 70, causing the circular portion 70 to exert a force that tends to contract the circular portion 70 (e.g., an inward radial force). Conversely, compression of the circular portion 70 beyond the relaxed position loads the circular portion 70 such that the circular portion 70 exerts a force to expand the circular portion 70 (e.g., an outward radial force).

The clamp 26 includes a pivot arm 72 and a travelling arm 74 that extend from the circular portion 70. The pivot arm 72 and the travelling arm 74 provide leverage to expand and contract the circular portion 70, thus opening and closing the clamp 26. The pivot arm 72 includes a pivot end 73, and the travelling arm 74 includes a travelling end 75. The ends 73, 75 extend generally perpendicular to their respective arms 72, 74. The ends 73, 75 each pass through the cam 28 and are captured in the cam 28 by a cap 76, 77.

Referring to FIGS. 5A to 5E, the cam 28 includes a top side 78, a bottom side 79, and opposite lateral sides 80, 81. The cam 28 can be formed of, for example, polyether ether ketone (PEEK) or stainless steel. The cam 28 defines a pivot hole 82 that admits the pivot end 73, and defines a channel 83 that admits the travelling end 75. About the pivot hole 82, in the top side 78, the cam 28 defines a recess 84 that receives the cap 76. Opposite the recess 84, the cam 28 includes a boss 89 that extends from the bottom side 79. The height, H, of the boss 89 maintains a space between the pivot arm 72 and the bottom side 79. By contrast, the travelling arm 74 can contact the bottom side 79. The two arms 72, 74 travel in different planes separated by the distance H. Because the boss 89 maintains the pivot arm 72 at a distance from the bottom side 79, the travelling arm 74 can move relative to the pivot arm 72 without contacting the pivot arm 72. The cap 77 is disposed adjacent to the top side 78 and the cap 76 is disposed in the recess 84 such that the caps 76, 77 do not contact each other during operation of the clamp 26.

The channel 83 defines a path, such as a curve, between a detent 85 and an end 86 located near the pivot hole 82. The detent 85 includes a hooked portion of the channel 83 that captures the travelling end 75 to secure the clamp 26 in the closed position.

The cam 28 includes an extension 87 that indicates proper placement of the cuff 20 relative to the pump 12. As the cuff 20 becomes coupled to the cannula 50, the extension 87 engages the surface 13 of the pump 12 to indicate proper placement of the cuff 20 relative to the pump 12. In addition, the extension 87 aligns the cam 28 in a plane generally parallel to the surface 13. Alignment of the cam 28 with respect to the surface 13 reduces the likelihood that the cam 28 may engage a portion of the pump 12 and improperly impede the clamp 26 from closing completely. The cam 28 also includes a raised portion 88 extending from the top side 78, which facilitates manipulation of the cam 28. The raised portion 88 is rounded to rest against the outer circumference of the pump 12 when the cam 28 is locked (see FIG. 9C). The raised portion 88 defines a slot 90 in which a tool or surgical instrument can be inserted to unlock the cam 28. The slot 90 can be used to pry open the clamp 26, for example, if tissue in-growth makes manual manipulation of the cam 28 difficult.

Manipulation of the cam 28 moves the clamp 26 between open and closed positions. In the open position, the clamp 26 permits a proximal portion 52 of the cannula 50 to pass through the opening 30. In the closed position, the clamp 26 presses inward to couple the cuff 20 to the cannula 50. In the closed position, the clamp 26 presses the linking member 24 into engagement with the cannula 50, and the circumferential inner surface 40 of the linking member 24 forms a seal with the cannula 50.

Referring to FIG. 2B, the cannula 50 is shown by itself here but is generally an integrated component of the pump 12. In some implementations, the pump 12 can receive different interchangeable cannulas to achieve an appropriate fit in a particular anatomy. The cannula 50 includes the proximal portion 52 that passes through the opening 30 into the heart 14 and a distal portion 54 housed within the pump 12. Along the length of the cannula 50, between the proximal portion 52 and the distal portion 54, the cannula 50 includes a circumferential tapered portion 56, a circumferential ridge 58, and a circumferential flange 62. The cannula 50 defines a circumferential groove 60 in which the clamp 26 and the linking member 24 are received.

To couple the cannula 50 to the cuff 20, the proximal portion 52 is passed through the opening 30, such that the circumferential tapered portion 56 engages the circumferential inner surface 40 of the linking member 24, guiding the cannula 50 into alignment with the cuff 20. Further advancement of the cannula 50 causes the circumferential ridge 58 to travel past the circular portion 70 of the clamp 26. The action of the circumferential ridge 58 passing the circular portion 70 provides a clinician tactile feedback about the proper location of the components. The circumferential flange 62 limits further travel of the cannula 50 relative to the cuff 20, positioning the circular portion 70 of the clamp 26 about the circumferential groove 60. The fastening member 22 is disposed about the cannula 50, generally about the circumferential ridge 58.

The cuff 20 is sized so that the inner diameter of the cuff 20 is greater than the outer diameter of the proximal portion 52, which facilitates insertion of the proximal portion 52. With the clamp 26 in its open position, the size of the inner diameter of the cuff 20 approximates that of the outer diameter of the circumferential ridge 58. The circumferential ridge 58 is rounded, permitting the linking member 24 to slide over the circumferential ridge 58 and into the circumferential groove 60. Thus a clinician can determine that the cuff 20 is properly positioned relative to the cannula 50 by experiencing the tactile sensation of the linking member 24 entering the circumferential groove 60.

Referring to FIG. 6, the cuff 20 is coupled to the cannula 50 by moving the clamp 26 to its closed position. In the closed position, the inner diameter of the clamp 26 is smaller than the outer diameter of the circumferential ridge 58. The clamp 26 presses the linking member 24 into the circumferential groove 60, forming a seal and capturing the cannula 50 in the cuff 20. The outer diameter of the cannula 50 at the circumferential groove 60 is larger than the outer diameter of the proximal portion 52. The differential in diameter allows passage of a coring tool through the cuff 20. In some instances, the coring tool can be slightly larger than the proximal portion 52 of the cannula 50. In addition, the differential in diameter can allow the clinician to further confirm proper placement of the cuff 20 relative to the cannula 50. A clinician can confirm proper placement by applying a small axial load that would tend to separate the cannula 50 from the cuff 20. If the cannula 50 and the cuff 20 separate easily, then the cuff 20 is improperly seated. If cannula 50 and the cuff 20 remain coupled, however, the cuff 20 is properly seated.

Referring to FIG. 7A, as the clamp 26 moves from the open position of FIG. 7A to the closed position of FIG. 7C, the cam 28 rotates about the pivot end 73 in a plane. As the cam 28 rotates, the travelling end 75 travels through the channel 83. In the open position, the pivot arm 72 and the travelling arm 74 are located near each other, and the circular portion 70 is expanded beyond its relaxed position. In this position, the clamp 26 can admit the circumferential ridge 58 of the cannula 50 through the opening 30. The travelling end 75 is located at the end 86 of the channel 83 nearest the pivot end 73.

Because the circular portion 70 is loaded, the circular portion 70 exerts a force on the end 75 in the direction of arrow F₁ to separate the pivot arm 72 and the travelling arm 74. Nevertheless, the open position is stable because the force acts away from the length of the channel 83 and instead presses the travelling end 75 into the end 86 of the channel 83. As a result, the open position can be maintained while the cannula 50 is placed relative to the clamp 26.

From the open position, a clinician closes the clamp 26 by exerting a force on the side 80 of the cam 28, causing the cam 28 to rotate in a plane about the pivot end 73. A small rotation of the cam 28 in the direction of arrow R₁ brings the length of the channel 83 into closer alignment with the direction of force, F₁, exerted by the circular portion 70 on the travelling end 75. The force exerted by the circular portion 70 continues the rotation of the cam 28 about the pivot end 73 as the clamp 26 continues to close.

Referring to FIG. 7B, the clamp 26 is in an unstable position between the open position and the closed position. Force exerted by the loaded circular portion 70 continues to rotate the cam 28 in the plane and close the clamp 26. The distance between the pivot arm 72 and the travelling arm 74 increases, and the circular portion 70 contracts, resulting in an overlap of the circular portion 70 of a distance, D₁. The clinician is not required to apply additional force on the cam 28 to move the clamp 26 to the closed position. The clamp 26 exerts a force in the direction of arrow F₂, moving the end 75 through the channel 83. As the travelling end 75 proceeds through the channel 83, the cam 28 continues to rotate about the pivot end 73, as indicated by arrow R₂.

Referring to FIG. 7C, with the clamp 26 in the closed position, the cannula 50 is captured within the clamp 26. The size of the circular portion 70 in the closed position can be selected to permit rotation of the cannula 50 relative to the cuff 20 or to limit such rotation.

The closed position is stable. The circular portion 70 is in its unloaded, relaxed position. As a result, the clamp 26 does not exert a force on the travelling end 75 in either direction along the channel 83. The travelling end 75 is located in the channel 83 near the detent 85 but not in the detent 85.

To lock the clamp 26, the clinician applies a force to the side 80 of the cam 28, in the direction of arrow C, which rotates the cam 28 further in the plane. As the cam 28 rotates, the cam 28 exerts a force on the travelling end 75 that is generally aligned with the channel 83, causing the arms 72, 74 to separate further. Rotation of the cam 28 moves the travelling end 75 into the detent 85 and loads the circular portion 70. This action closes the circular portion 70 beyond its relaxed position, reducing the diameter of the circular portion 70 to lock the clamp 26 about the circumferential groove 60 of the cannula 50. Locking the clamp 26 also causes the circular portion 70 to exert an inward radial force to compress the linking member 24 and press the circumferential inner surface 40 into the circumferential groove 60, forming a hemostatic seal.

Referring to FIG. 7D, in the locked position of the clamp 26, the cam 28 impedes the clamp 26 from opening. The circular portion 70 is slightly compressed beyond its relaxed position, such that the overlap distance D₃ is larger than D₂. The loaded circular portion 70 exerts a force on the travelling end 75 in the direction of arrow F₃, which presses the travelling end 75 into the detent 85. Because the circular portion 70 forces the travelling end 75 into the detent 85, the travelling end 75 is impeded from traveling through the channel 83 and moving the clamp 26 into the open position.

To open the clamp 26 from the locked position, the travelling end 75 must be dislodged from the detent 85. The clinician applies a force, for example, in the direction of arrow U, to overcome the force of the loaded circular portion 70. The force rotates the cam 28 in the plane such that the travelling end 75 slides out of the detent 85.

From the closed position (FIG. 7C), the clamp 26 can be opened by exerting a force on the side 81 away from the circular portion 70, which rotates the cam 28 opposite the direction of arrows R₁ and R₂ until the open position is reached. The cannula 50 can then be removed or repositioned relative to the clamp 26 before the clamp 26 is closed again.

Referring to FIG. 8A, the cuff 20 is in the open position before being coupled to the cannula 50 of the pump 12. Generally, during the implantation process, the cuff 20 will first be attached to the heart 14 and then heart tissue will be removed to admit the proximal portion 52 of the cannula 50. In addition, or alternatively, heart tissue can also be removed before the cuff 20 is attached to the heart 14.

The cannula 50 is fixedly coupled to the pump 12, for example, the cannula 50 can be sealed and welded to the pump 12. Alternatively, the cannula 50 can be removably coupled to the pump 12, for example, by a threaded connection or by a mechanism that permits the cannula 50 to snap into place. A clinician can select a cannula 50 that best fits the anatomy of the patient, and can couple the cannula 50 to the pump 12 prior to or during a procedure. When the cannula 50 is coupled to the pump 12, the distal portion 54 is housed within the pump 12 and the proximal portion 52 extends from a top surface 13 of the pump 12. A clinician may select a cannula 50 that extends an appropriate distance into the heart 14. For example, a clinician may a cannula 50 with a first length for a left VAD so that the cannula 50 extends the proper distance into the heart 14. For implantation of a right VAD, however, the clinician may use a cannula with a different length so that the cannula extends a different distance into a heart.

To couple the cannula 50 to the cuff 20, the pump 12 and the cannula 50 are advanced toward the cuff 20 so that the proximal portion 52 of the cannula 50 enters the opening 30. As the cannula 50 travels relative to the cuff 20, the circumferential ridge 58 engages the circumferential inner surface 40 of the linking member 24. Further travel of the cannula 50 relative to the cuff 20 advances the circumferential ridge 58 through the linking member 24, so that the clamp 26 and the linking member 24 are disposed about the circumferential groove 60.

Advancing the circumferential ridge 58 through the linking member 24 produces tactile feedback for the clinician, such as a snap-like sensation. The tactile feedback indicates that the cuff 20 is properly seated against the circumferential flange 62 and that the circular portion 70 is disposed about the circumferential groove 60. In some implementations, as the circumferential ridge 58 engages the linking member 24 disposed over the circular portion 70, the circumferential ridge 58 slightly expands the circular portion 70. When the circumferential ridge 58 passes through the clamp 26, the clamp 26 contracts to its open position, contributing to the tactile feedback experienced by the clinician.

Referring to FIGS. 8B and 9A, the cuff 20 is disposed about the cannula 50, with the linking member 24 partially disposed in the circumferential groove 60. In this position, the clamp 26 can be closed to capture the cannula 50 in the cuff 20. To close the clamp 26, the clinician manipulates the cam 28 to begin rotating the cam 28 about the pivot end 73, in the direction of arrow R₃.

Referring to FIGS. 8C and 9B, the resilient force of the clamp 26 moves the travelling end 75 through the channel 83 defined in the cam 28, continuing the rotation of the cam 28 about the pivot end 73, in the direction of arrow C₁. The circular portion 70 of the clamp 26 contracts and presses the linking member 24 into the circumferential groove 60. The contraction of the circular portion 70 captures the cannula 50 within the cuff 20 because the circumferential ridge 58 cannot pass through the circular portion 70.

Referring to FIGS. 8D and 9C, the clamp 26 is in a closed position and the cam 28 is in a locked position, maintaining the clamp 26 in the closed position. The travelling end 75 of the clamp 26 is located in the detent 85 defined in the cam 28. From this position, the clamp 26 is unlikely to be opened accidentally, because significant force is required to remove the travelling end 75 from the detent 85. The top side 78 of the cam 28 is disposed against the top surface 13 of the pump 12, and the raised portion 88 of the cam 28 rests against the outer circumference of the pump 12.

Referring to FIG. 10A, implantation of pump 12 to the heart 14 can include selecting a location to attach the cuff 20. For example, the apex 15 of the left ventricle can be selected as an operation site.

Referring to FIG. 10B, the cuff 20 is placed in contact with the heart 14 at the selected operation site. The cuff 20 is attached to the heart 14, for example, with sutures. In some embodiments, a cardiac bypass system is activated so that blood does not circulate through the heart 14. A core section of heart tissue is removed through the opening 30 of the cuff 20. Alternatively, in some embodiments, the cuff 20 can be attached to the heart 14 and a core section of heart tissue can be removed in the absence of a cardiac bypass. As another alternative, in some implementations, the core section of heart tissue can be removed before attaching the cuff 20 to the heart 14.

Referring to FIG. 10C, heart tissue has been removed so that the proximal portion 52 can be admitted through the opening 30 of the cuff 20. The clamp 26 of the cuff 20 is moved to its open position (not shown) and the proximal portion 52 of the cannula 50 is received through the opening 30.

Referring to FIG. 10D, the proximal portion 52 advances through the opening 30 until the circular portion 70 of the clamp 26 is disposed about the circumferential groove 60. The clinician determines that the circular portion 70 is located about the circumferential groove 60 based on (i) snap-like tactile feedback of the circumferential ridge 58 passing through the linking member 24 and (ii) engagement of the linking member 24 to the circumferential flange 62. The clinician couples the cuff 20 to the cannula 50 by rotating the cam 28 in a plane generally parallel to the top surface 13 of the pump 12. Rotation of the cam 28 moves the clamp 26 to its closed position, in which the cannula 50 is captured within the cuff 20. The clinician rotates the cam 28 further in the plane to engage the locking mechanism of the cam 28, impeding the clamp 26 from leaving the closed position. By engaging the locking mechanism of the cam 28, orientation of the cuff 20 to the cannula 50 can be secured such that axial movement of the cannula 50 relative to the cuff 20 and rotation of the cannula 50 relative to the cuff 20 are both impeded.

The size of the cuff 20 can be selected such that, when the pump 12 is coupled to the cuff 20, the distance between the heart 14 and the top surface 13 of the pump 12 is small. For example, the total height of the cuff 20 may be, for example, between approximately 2 mm and approximately 10 mm. Because the cam 28 can be moved to a locked position by planar movement, the locking mechanism does not require clearance between the cuff 20 and the top surface 13.

In addition, the inflow cannula 50 can define two or more circumferential grooves between two or more circumferential ridges. Multiple circumferential grooves can provide different locations along the length of the cannula 50 at which the cuff 20 can be coupled. A clinician couple the cuff 20 at a particular circumferential groove to select the distance that the cannula 50 will extend into the heart 14.

The thickness of the fastening member 22 can be selected to adjust the length that the cannula 50 extends into the heart 14. The use of a thicker fastening member 22 can result in the cannula 50 extending a shorter depth into the heart 14 than the use of a thinner fastening member 22. A clinician may select a cuff 20 that includes a fastening member 22 of an appropriate thickness to set the distance that the cannula 50 extends into the heart 14.

A clinician may also adjust the distance that the cannula 50 extends into the heart by adding one or more spacers, such as a ring-shaped fabric washer, between the cuff 20 and the heart 14. For example, a clinician may place a spacer between the surface of the heart 14 and the contact surface 23 of the fastening member 22. Sutures can be placed through the fastening member 22 and through the spacer to attach the cuff 20 at an appropriate distance from the heart 14.

In some implementations, the length of the proximal portion 52 of the cannula 50 can be varied to achieve a desired length of extension of the proximal portion 52 into the heart 14. For example, several inflow cannulas having proximal portions of different lengths can be fabricated. A clinician can select an inflow cannula that has a proximal portion corresponding to the desired length of extension into the heart of a particular patient, and can couple the selected inflow cannula to a pump before or during a procedure.

As an alternative to the clamp 26, the cuff 20 may include a resilient metal split ring. A break or gap in the split ring permits the diameter of the split ring to expand as it travels over the circumferential groove 58 of the cannula 50. Once the split ring is located about the circumferential groove 60, the split ring contracts into the circumferential groove 60 to couple the cuff 20 to the cannula 50. The split ring may thus be operated without arms extending from the split ring and without a cam.

Referring to FIGS. 11A and 11B, an alternative cuff 120 and an alternative cannula 150 can be used to couple a pump 250 (FIG. 14A) to heart tissue. A coupling mechanism, for example, an attachment member 126, couples the cuff 120 to the cannula 150. A locking mechanism in the form of a clip 200 (FIG. 13A) impedes the cuff 120 from becoming uncoupled from the cannula 150.

The cuff 120 defines an opening 130 that admits a proximal portion 152 of the cannula 150. The cuff 120 includes an annular fastening member 122, a linking member 124, and the attachment member 126. The fastening member 122 can be sutured to heart tissue, and can include, for example, a fabric such as PTFE felt.

The linking member 124 is formed of, for example, an elastomer such as silicone, and includes a reinforcement member 128 (FIG. 16) such as a mesh ring. The linking member 124 is disposed about an outer circumference of the attachment member 126 and serves as a linking member to couple the attachment member 126 to the fastening member 122, as discussed further below. The linking member 124 is coupled to the fastening member 122 by, for example, sutures. The linking member 124 can also be molded directly to the fastening member 122. The linking member 124 includes a bottom surface 125 configured to engage a generally flat circumferential flange 162 of the cannula 150, forming a face seal with the circumferential flange 162.

The cannula 150 includes the proximal portion 152 that enters the opening 130 of the cuff 120 and a distal portion 154 that is housed in the pump 250. The cannula 150 includes a first circumferential taper 156 that engages extensions 136 of the attachment member 126 and deflects them away from the cannula 150 as the cannula 150 advances through the opening 130. The cannula 150 includes a second circumferential taper 158 and defines a circumferential groove 160 between the second circumferential taper 158 and the circumferential flange 162.

Referring to FIGS. 12A and 12B, the attachment member 126 is formed of, for example, a rigid material such as metal. The attachment member 126 includes a ring portion 132 having a wall 133 with cutouts 134 that define flexible extensions 136. Each extension 136 includes a lower tapered portion 138 (FIG. 12B) disposed on a free end 139 of the extension 136, facing inward toward the opening 130. As the first circumferential taper 156 of the cannula 150 is inserted through the opening 130, the lower tapered portions 138 engage the first circumferential taper 156, causing the extensions 136 to flex outward from the opening 130 and permit the first circumferential taper 156 to pass through the opening 130. When the lower tapered portions 138 are disposed in the circumferential groove 160, the lower tapered portions 138 engage the second circumferential taper 158 of the cannula 150 to impede the cannula 150 from easily exiting the cuff 120. Each lower tapered portion 138 includes upper tapered portion 140, and the width of each lower tapered portion 138, W, decreases along the length of each lower tapered portion 138, between the upper tapered portion 140 and the free end 139.

The extensions 136 can have equal sizes or can be selected to have differing sizes. For example, asymmetrical lengths of the extensions 136 can cause the extensions 136 to engage the circumferential tapers 156, 158 sequentially rather than consecutively during travel of the cannula 150 relative to the cuff 120, reducing the force required to couple the cannula 150 to the cuff 120 or to uncouple the cannula 150 from the cuff 120.

The amount of force required to deflect the extensions is correlated with the angle of the taper of the circumferential tapers 156, 158 and the tapered portions 138, 140. The steepness of the taper angles can be selected such that different amounts of force along the length of the cannula 150 are required to couple the cuff 120 to the cannula 150 can remove the cuff 120 from the cannula 150. The engagement of tapers with a steep angle result in a lower percentage of axial force being transmitted radially outward than the engagement of shallower tapers. Thus to allow the cuff 120 to be coupled to the cannula 150 with a smaller force than the force required to remove the cuff 120 from the cannula 150, the tapers of the lower tapered portions 138 and the circumferential taper 156 are less steep than the tapers of the upper tapered portions 140 and the circumferential taper 158. Accordingly, more force is required to decouple the cuff 120 than to couple the cuff 120 to the cannula 150. The amount of force required to couple the cuff 120 to and decouple the cuff 120 from the cannula 150 can be adjusted by the materials selected for the attachment member 126, the thickness of the extensions 136, the length and width of the extensions 136, and the geometry of the cutouts 134.

The attachment member 126 includes flanged portions 146, disposed between the extensions 136 along the outer circumference of the attachment member 126, at the bottom 141 of the attachment member 126. The flanged portions 146 extend generally perpendicular to the wall 133. When the cuff 20 is coupled to the cannula 150, the flanged portions 146 are disposed in a plane generally parallel to the circumferential flange 162 of the cannula 150. When the cuff 20 is locked to the cannula 150, the flanged portions 146 are captured between the clip 200 and the circumferential flange 162, impeding the cuff 120 from becoming uncoupled from the cannula 150.

The flanged portions 146 define holes 148 through which material of the linking member 124 is molded or adhesive is applied to form mechanical locks that secure the linking member 124 to the attachment member 126. Material of the linking member 124 is also molded or adhesively bonded through the cutouts 134 and over the ring portion 132. For example, silicone can be molded over the attachment member 126 and can be molded over a portion of the fastening member 122. The linking member 124 can also be coupled to the attachment member 126 with adhesive or sutures. The linking member 124 covers the flanged portions 146, an outer surface 142 of the wall 133, and a portion of an inner surface 144 of the wall 133 (FIG. 16).

The flanged portions 146 and extensions 136 are disposed symmetrically along the circumference of the attachment member 126, permitting the extensions 136 to engage the circumferential tapers 156, 158 evenly about the cannula 150, and permitting the flanged portions 146 to evenly press the bottom surface 125 of the linking member 124 into engagement with the circumferential flange 162. The attachment member 126 can include more or fewer flanged portions 146 and extensions 136 than those illustrated.

To couple the cannula 150 to the cuff 120, a clinician inserts the proximal portion 152 of the cannula 150 through the opening 130. As the cannula 150 advances through the opening 130, the first circumferential taper 156 passes the upper tapered portion 140 of the lower tapered portions 138. The engagement of the lower tapered portions 138 with the first circumferential taper 156 (which resists advancement of the cannula 150 by deflecting the extensions 136) ends abruptly, permitting the extensions 136 to straighten so that the lower tapered portions 138 reside in the circumferential groove 160. The sudden decrease in resistance to advancement of the cannula 150 produces a tactile snap-like sensation, indicating to the clinician that the cannula 150 is coupled to the cuff 120. The upper tapered portion 140 of the lower tapered portions 138 engage the second circumferential taper 158, impeding the cannula 150 from separating from the cuff 120. The bottom surface 125 of the linking member 124 engages the circumferential flange 162, limiting further advancement of the cannula 150 relative to the cuff 120.

After the cannula 150 and cuff 120 are coupled, the cannula 150 can be separated from the cuff 120 by a force sufficient to deflect the extensions 136. Engagement of the upper tapered portions 140 with the second circumferential taper 158 deflects the extensions 136, allowing the cannula 150 to be removed from the cuff 120.

Referring to FIGS. 13A and 13B, the clip 200 is used to secure the cuff 120 about the cannula 150. The clip 200 cooperates with features of the pump 250, described below, to limit travel of the cuff 120 relative to the cannula 150. The clip 200 includes a top side 202, a bottom side 204, and opposite lateral sides 206, 208. The clip 200 can be formed of, for example, a rigid plastic, such as PEEK, or metal, such as titanium.

The clip 200 includes guide rails 212 and arms 214, and defines a recess or opening 215 or opening. The guide rails 212 guide the clip 200 through a linear motion as the clip 200 is received by the pump 250. The opening 215 admits a tool or a finger of the clinician to facilitate disengagement of the clip 200 from its locked position relative to the cuff 120. The arms 214 are curved and resilient, and define an opening 220. As the clip 200 moves relative to the pump 250, the pump 250 forces the arms 214 laterally outward, expanding the opening 220 and allowing the arms 214 to extend about the linking member 124 of the cuff 120. In the locked position of the clip 200, the pump 250 forces the arms 214 laterally inward to engage the linking member 124 and to secure the cuff 120 to the pump 250.

The arms 214 include teeth 216 that extend from inner walls 217 of the arms 214 toward the opening 220. In the locked position of the clip 200, the teeth 216 are disposed over the flanged portions 146 of the attachment member 126, thus capturing the flanged portions 146 between the teeth 216 and the circumferential flange 162 of the cannula 150. Between the teeth 216 are gaps 218 that permit the arms 214 to flex laterally as the clip 200 is received by the pump 250. When the clip 200 is in a locked position about the cuff 120, the teeth 216 engage the linking member 124 of the cuff 120 to impede rotation of the cuff 120 relative to the clip 200 and the pump 250.

Each arm 214 includes a post 219 extending from the bottom side 204 that is received in one of the channels 254 (FIG. 14A) defined by the pump 250. As the pump 250 receives the clip 200, the posts 219 travel through the channels 254, directing the lateral flexion of the arms 214. The posts 219 each include angled walls 221, 222 (FIG. 13C) that engage angled walls 257, 258 (FIG. 16) of the pump 250 that define the channels 254, capturing the posts 219 in the channels 254.

Referring to FIG. 14A, the pump 250 is coupled to the cannula 150 and receives a clip 200. The pump 250 defines generally parallel slots 252 that receive the guide rails 212 of the clip 200. The pump 250, in a top side 256, also defines the channels 254 that receive the posts 219 between the angled walls 257, 258 (FIG. 16). The angled walls 257, 258 capture the posts 219, impeding the posts 219 from leaving the channels 254 and maintaining the arms 214 in a plane above the top side 256. The portion of the pump 250 that defines the channels 254 can be an integral component of, for example, a motor housing of the pump, or can be a separate component that attaches to the pump 250, for example, with welds, screws, or other fastening mechanisms.

The pump 250 defines an entry recess 255 at each channel 254 that admits the post 219. The distance between the entry recesses 255 is larger than the distance between the posts 219 when the arms 214 of the clip 200 are not flexed.

To insert the posts 219 into the channels 254, the clinician flexes the arms 214 outward, loading the resilient arms 214 and permitting the posts 219 to enter the channels 254 at the entry recesses 255. After the posts 219 are positioned in the entry recesses 255, the arms 214 flex inward to their natural resting condition, moving the posts 219 in the channels 254 away from the entry recesses 255. Because the posts 219 are captured in the channels 254, the clip 200 will not separate from the pump 250 until the clinician flexes the arms 214 outward and upward, permitting the posts 219 to leave the channels 254 at the entry recesses 255. The pump 250 can be provided with the clip 200 already positioned in the channels 254, and thus already captured by the pump 250, to streamline the implantation procedure.

A first portion 260 of the channels 254 curves outward about the cannula 150 to spread the arms 214, permitting the arms 214 to extend about the cannula 150 and the linking member 124 of the cuff 120. A second portion 262 of the channels 254 curves inward toward the cannula 150, moving the arms 214 inward about the cannula 150.

Referring to FIG. 14B, the guide rails 212 of the clip 200 enter the slots 252, and the posts 219 are captured in the channels 254. The clip 200 travels in a generally linear direction relative to the pump 250, in the direction of arrow I₁, until the clip 200 reaches the position of FIG. 14C. As the clip 200 is advanced into the pump 250, the force in the direction of arrow I₁ causes the posts 219 to deflect outward in the channels 254. Once the posts 219 have reached the peak distance between the channels 254, the insertion force required in the direction of arrow lessens as the inward deflection force of the arms 214 drive the clip 200 through the second portion 262 of the channels 254. The clip 200 travels linearly as the posts 219 travel through the channels 254, until the position of FIG. 14C is reached in which the arms 214 are in their relaxed position.

To move the clip 200 back to the unlocked position, the clip 200 is retracted in a direction opposite the arrow I₁, and the posts 219 travel in the opposite direction through the channels 254. During removal of the clip 200, the second portion 262 expands the arms 214 and the first portion 260 permits the arms 214 to become closer together. The angle of the first portion 260 is less steep than the angle of the second portion 262, which results in the force to remove the clip 200 being higher than the force to move the clip 200 into the locking position.

Referring to FIG. 15A, a clinician moves the pump 250 and the cannula 150 relative to the cuff 120, in the direction of arrow B, so that the proximal portion 152 enters the opening 130 of the cuff 120. As the cannula 150 advances, the first circumferential taper 156 deflects the extensions 136 away from the cannula 150. The first circumferential taper 156 and the second circumferential taper 158 advance past the tapered portions 138 of the extensions 136. As the first circumferential taper 156 advances past the tapered portions 138, the deflected extensions 136 straighten, forcing the tapered portions 138 into the circumferential groove 160. The clinician experiences tactile feedback, such as a snap-like sensation, that indicates that the cannula 150 is coupled to the cuff 120. The bottom surface 125 of the linking member 124 engages the circumferential flange 162 of the cannula 150. In some implementations, the bottom surface 125 engages a surface of the pump 250 as an alternative to, or in addition to, engaging a portion of the cannula 150.

Referring to FIG. 15B, the clinician advances the clip 200 into the pump 250. The guide rails 212 of the clip 200 travel in the slots 252, guiding the clip 200 as it travels linearly in a plane above the top side 256, in the direction of arrow 12. As the clip 200 travels relative to the pump 250, the arms 214 flex laterally due to engagement of the posts 219 with the angled walls 257, 258 defining the channels 254. The arms 214 move laterally outward to admit the linking member 124 and then laterally inward to engage the linking member 124.

Referring to FIG. 15C, the clip 200, in its locked position, limits travel of the cuff 120 relative to the cannula 150. The engagement of the posts 219 with the angled walls 257, 258 that define the channels 254 forces the arms 214 inward such that the teeth 216 of the arms 214 are disposed over the flanged portions 146 of the attachment member 126. The flanged portions 146 are captured between the teeth 216 and the circumferential flange 162. The engagement of the teeth 216 to the linking member 124 presses the bottom surface 125 against the circumferential flange 162, forming a seal (FIG. 16).

In an implanted state, after the clip 200 is in its locked position, the pump 250 and the cannula 150 are in a position suitable for long-term stability relative to the cuff 120 and the heart. While the clip 200 is in its locked position, an extremely large force is required to remove the cuff 120 from the cannula 150. For example, the force required to forcibly separate the pump 250 or cannula 150 from the cuff 120 while the clip 200 is in its locked position can be as large as the force required to tear the cuff 120 from the heart.

The distance that the cannula 150 extends into a heart can be selected in a similar manner as described above. For example, a cannula 150 with a proximal portion 152 having a particular length can be selected, one or more spacers can be placed between the fastening member 122 and a heart, or the thickness of the fastening member 122 can be selected for a particular patient.

Referring to FIGS. 17A and 17B, an alternate implementation includes a cuff 320 and a cannula 350 configured to cooperate with the pump 250 and the clip 200. The cuff 320 defines an opening 330 that admits a proximal portion 352 of the cannula 350. A coupling mechanism in the form of an attachment member 326 engages a sealing ring 502 (FIG. 19A), such as an o-ring, disposed about the cannula 350 to couple the cuff 320 to the cannula 350. The clip 200 (FIG. 13A) acts as a locking mechanism to impede the cuff 320 from becoming uncoupled from the cannula 350.

The cuff 320 includes an annular fastening member 322 that a clinician can fasten to heart tissue. For example, the fastening member 322 can be formed of a fabric such as PTFE felt. The cuff 320 includes a linking member 324 coupled to the fastening member 322, for example, by sutures or direct molding. The linking member 324 is formed of, for example, an elastomer such as silicone. The linking member 324 includes a reinforcement member 325 (FIG. 18B), such as a mesh ring. The linking member 324 couples the attachment member 326 to the fastening member 322, as described below.

The linking member 324 includes a bottom surface 328 that engages a circumferential flange 362 of the cannula 350. The primary sealing mechanism between the cuff 320 and the cannula 350 is the sealing ring 502, and as a result, the linking member 324 and the circumferential flange 362 are not required to form a seal. Nevertheless, in some implementations, the linking member 324 may form a secondary seal with the circumferential flange 362. In some implementations, the bottom surface 328 engages a surface of the pump 250 as an alternative to, or in addition to, engaging a portion of the cannula 350.

The cannula 350 includes the proximal portion 352, the circumferential flange 362, and a distal portion 354 housed within the pump 250. The cannula 350 includes a circumferential taper 356 that engages a circumferential taper 405 of the attachment member 326, guiding the cuff 320 into alignment with the cannula 350. The cannula 350 defines a circumferential groove 360 between a first circumferential ridge 358 and a second circumferential ridge 359. The circumferential groove 360 receives the sealing ring 502.

Referring to FIGS. 18A and 18B, the attachment member 326 is formed of, for example, a rigid material such as metal or PEEK. The attachment member 326 includes a cylindrical portion 402, which defines an inner circumferential groove 404 that admits a portion of the sealing ring 502. The sealing ring 502 is formed of, for example, an elastomer such as silicone or implantable-grade ethylene propylene diene monomer (EPDM). In some implementations, the attachment member 326 does not define an inner circumferential groove 404 and instead has a substantially cylindrical inner surface.

The attachment member 326 includes a flanged portion 406, for example, a circumferential flange that extends in a plane generally perpendicular to an outer wall 403 of the cylindrical portion 402. The attachment member 326 includes the inner circumferential taper 405 that engages the sealing ring 502, compressing the sealing ring 502 and permitting the sealing ring 502 to enter the inner circumferential groove 404.

The linking member 324 is molded over the attachment member 326, and the flanged portion 406 and the cylindrical portion 402 define holes 407 that admit material of the linking member 324. The material of the linking member 324 that extends through the holes 407 forms mechanical locks that couple the linking member 324 to the attachment member 326. The linking member 324 is molded over an inner circumferential wall 408 and an outer circumferential surface 410 of the cylindrical portion 402, as well as a top surface 412, a bottom surface 414, and a circumferential side surface 416 of the flanged portion 406.

Referring to FIGS. 19A and 19B, the sealing ring 502 is disposed in the circumferential groove 360. To couple the cannula 350 to the cuff 320, the clinician moves the proximal portion 352 through the opening 330 of the cuff 320. The sealing ring 502 engages the circumferential taper 405 of the attachment member 326, compressing the sealing ring 502 into the circumferential groove 360.

As the cannula 350 advances through the opening 330, the sealing ring 502 advances past the circumferential taper 405 to the position of FIG. 19B. The sealing ring 502 expands into the circumferential groove 404 of the attachment member 326 and the bottom surface 328 of the linking member 324 engages the circumferential flange 362. The sealing ring 502 is partially disposed in the circumferential groove 404 and partially disposed in the circumferential groove 360 of the cannula 350. The engagement of the sealing ring 502 between the cuff 320 and the cannula 350 limits travel of the cannula 350 relative to the cuff 320, coupling the cannula 350 to the cuff 320. The expansion of the sealing ring 502 into the circumferential groove 404 provides snap-like tactile feedback to the clinician, indicating that the cannula 350 is coupled to the cuff 320. The sealing ring 502 also creates a hemostatic seal between the cannula 350 and the cuff 320.

From the position of FIG. 19B, the clinician can move the clip 200 into a locked position about the cuff 320 as described above with reference to FIGS. 14A to 14C. With the clip 200 in its locked position (FIG. 20), the flanged portion 406 is captured between the clip 200 and the circumferential flange 362, impeding the cuff 320 from becoming separated from the cannula 350.

The distance that the cannula 350 extends into a heart can be selected in a similar manner as described above. For example, a cannula 350 with a proximal portion 352 having a particular length can be selected, one or more spacers can be placed between the fastening member 322 and a heart, or the thickness of the fastening member 322 can be selected for a particular patient.

Referring to FIG. 21, an alternate implementation include a cuff 620 that couples to a cannula 650 of a pump 750. The cuff 620 defines an opening 630 that admits a proximal portion 652 of the cannula 650. A coupling mechanism in the form of an attachment member 626 engages a sealing ring 802 (FIG. 23B), for example, an o-ring disposed about the cannula 650, to couple the cuff 620 to the cannula 650. A clip 700 (FIG. 25A) acts as a locking mechanism to impede the cuff 620 from becoming uncoupled from the cannula 650.

Like the implementations described above, the cuff 620 can be coupled to the pump 750 with a low profile, for example, in a distance from a heart that is approximately the height of the cuff 620 along the cannula 650. The cuff 620 is coupled to the pump 750 by moving the cannula 650 axially through the cuff 620. The locking mechanism, for example, the clip 700, can then be engaged to secure the position of the cuff 620 about the cannula 650. Similar to the cam 28 and the clip 200, the clip 700 moves into a locked position by moving in a plane perpendicular to a cannula, which facilitates attachment of the cuff 620 to the pump 750 in the low profile.

Referring to FIGS. 22A and 22B, the cuff 620 includes an annular fastening member 622 that a clinician can fasten to heart tissue. For example, the fastening member 622 can be formed of a fabric such as PTFE felt. The cuff 620 includes a linking member 624 coupled to the fastening member 622, for example, by sutures or direct molding. The linking member 624 is formed of, for example, an elastomer such as silicone. The linking member 624 includes a reinforcement member 625 (FIG. 22D), such as a mesh ring. The linking member 624 couples the attachment member 626 to the fastening member 622, as described below.

The linking member 624 includes a bottom surface 628 that engages a circumferential flange 662 (FIG. 23B) of the cannula 650. The primary sealing mechanism between the cuff 620 and the cannula 650 is the sealing ring 802, and as a result, the linking member 624 need not form a seal about the cannula 650. Nevertheless, in some implementations, the linking member 624 may form a secondary seal through engagement with the circumferential flange 662. In some implementations, the bottom surface 628 engages a surface of the pump 750 as an alternative to, or in addition to, engaging a portion of the cannula 650.

The linking member 624 defines a circumferential groove 632 in the outer diameter of the cuff 620, located between the fastening member 622 and a flanged portion 634 of the linking member 624. The circumferential groove 632 receives a portion of the clip 700 to secure the cuff 620 to the pump 750, as described further below. The linking member 624 includes ridges 636 in the circumferential groove 632, for example, disposed on the flanged portion 634. The ridges 636 are spaced apart and extend approximately halfway along the height, H₂, of the circumferential groove 632. When the clip 700 is in a locked position about the cuff 620, the clip 700 engages the ridges 636 to limit rotation of the cuff 620 about the cannula 650.

Referring to FIG. 22C, the attachment member 626 is formed of, for example, a rigid material such as metal or PEEK. The attachment member 626 includes a cylindrical portion 640 that has an outer wall 644 and an inner surface 642 that engages the sealing ring 802. The attachment member 626 includes a flanged portion 646, for example, a circumferential flange that extends in a plane generally perpendicular to the outer wall 644.

Referring to FIG. 22D, the linking member 624 is molded over the attachment member 626. The flanged portion 646 and the cylindrical portion 640 define holes 647 that admit material of the linking member 624. The material of the linking member 624 that extends through the holes 647 forms mechanical locks that couple the linking member 624 to the attachment member 626. The linking member 624 is molded over an inner circumferential wall 648, which can have a larger inner diameter than the rest of the cylindrical portion 640. The linking member 624 is also molded over an outer circumferential surface 610 of the cylindrical portion 640, as well as a top surface 612, a bottom surface 614, and a circumferential side surface 616 of the flanged portion 646. The inner surface 642 of the attachment member 626 remains exposed.

Referring to FIGS. 23A and 23B, the cannula 650 includes the proximal portion 652, the circumferential flange 662, and a distal portion 654 housed within the pump 750. The cannula 650 includes a circumferential taper 656 that engages the attachment member 626, guiding the cuff 620 into alignment with the cannula 650. The cannula 650 defines a circumferential groove 660 between a first circumferential ridge 658 and a second circumferential ridge 659. The sealing ring 802 is disposed in the circumferential groove 660 and is formed of, for example, an elastomer such as silicone or implantable-grade EPDM.

To couple the cannula 650 to the cuff 620, the clinician moves the proximal portion 652 through the opening 630 of the cuff 620 (FIG. 23A). As the cannula 650 advances further, the sealing ring 802 engages the inner surface 642 of the attachment member 626, compressing the sealing ring 802 into the circumferential groove 660 (FIG. 23B). The engagement of the sealing ring 802 with the inner surface 642 and the engagement of the bottom surface 628 with the circumferential flange 662 provide tactile feedback to the clinician that the appropriate position has been achieved.

The engagement of the sealing ring 802 between the cuff 620 and the cannula 650 limits travel of the cannula 650 relative to the cuff 620, coupling the cannula 650 to the cuff 620. The compression of the sealing ring 802 between the cuff 620 and the cannula 650 also creates a hemostatic seal between the cannula 650 and the cuff 620. From the position shown in FIG. 23B, the clinician can move the clip 700 into a locked position about the cuff 620 to secure the cuff 620 about the cannula 650, as described further below.

Referring to FIG. 24A, the sealing ring 802 has a cross-section 810 that is substantially trapezoidal. The force required to insert the cannula 650 into the cuff 620 using the sealing ring 802 is typically smaller than the force required to insert the cannula 650 using a sealing ring that has a round cross-section and a similar cross-sectional width. In some instances, a lower insertion force is desirable to facilitate installation of the cannula 650 relative to the implanted cuff 620.

The cross-section 810 has an inner side 811, and outer side 812, a top side 813, and a bottom side 814. Adjacent sides 811, 812, 813, 814 are connected by rounded corners 815. The inner side 811 faces toward the cannula 650 and is substantially flat. As a result, the inner surface of the sealing ring 810 is substantially cylindrical. The top side 813 faces away from the pump 750, and the bottom side 814 faces toward the pump 750. The top side 813 and the bottom side 814 are substantially parallel to each other, for example, both sides 813, 814 are substantially perpendicular to the inner side 811.

The top side 813 and the bottom side 814 have different lengths. The length, L₁, of the top side 813 can be, for example, between one-fourth and three-fourths of the length, L₂, of the bottom side 814. For example, the length, L₁, of the top side 813 can be approximately half or approximately two-thirds of the length, L₂, of the bottom side 814. The outer side 812 is angled, for example, forming substantially straight angled edge.

Referring to FIG. 24B an alternative sealing ring has a cross-section 860. The cross-section 860 includes an upper portion 862 and a lower portion 864, connected by a narrow neck 866. The sealing ring 850 thus includes two stacked discs, connected by an annular band. The cross-section 860 includes outer sides 870 engage the inner surface 642 of the cuff 620, and inner sides 872 that engage the cannula 650 in the circumferential groove 660.

Referring to FIGS. 25A and 25B, the clip 700 cooperates with features of the pump 750, described below, to limit movement of the cuff 620 (not shown) relative to the cannula 650. The clip 700 has an unlocked position, in which the cuff 620 can be coupled about the cannula 650. The clip 700 also has a locked position, in which the clip 700 secures the cuff 620 relative to the cannula 650. A component, such as a motor housing 753 or an element attached to the motor housing 753, provides an upper surface 752 that defines channels 754. The clip 700 includes arms 714 that extend into the channels 754 and travel along the channels 754 as the clip 700 moves into its locked position.

The pump 750 captures the clip 700 between the upper surface 752 and a cover 770. The cover 770 is attached over the upper surface 752 by, for example, screws 772 or welds. The upper surface 752 and the cover 770 define a slot 740 for the clip 700 to travel within. The slot 740 permits the clip 700 to travel in a plane, for example, to travel in a linear direction, A, in a plane perpendicular to a longitudinal axis, Y, of the cannula 650.

Referring to FIGS. 26A-26C, the clip 700 includes a top side 702 that faces the cover 770, a bottom side 704 that faces the upper surface 752, and opposite lateral sides 706, 708. The clip 700 can be formed of, for example, metal, such as titanium, or a rigid plastic, such as PEEK. The clip 700 includes guide rails 712 and defines a recess or opening 715. The guide rails 712 stabilize the clip 700 laterally and guide the clip 700 through a linear motion in the slot 740. The opening 715 admits a tool or a finger of the clinician to facilitate retraction of the clip 700.

The arms 714 of the clip 700 are curved and define an opening 720. The arms 714 are resilient and can deflect laterally to capture the cuff 620. Each arm 714 includes a post 719 that extends from the bottom side 704 of the clip 700. Each post 719 is received in one of the channels 754 (FIG. 25B) defined in the upper surface 752. The posts 719 are substantially cylindrical and extend perpendicular to, for example, a plane defined along the top side 702 of the clip 700. When the clip 700 is located in the slot 740, the posts 719 extend substantially parallel to the longitudinal axis, Y, of the cannula 650. As the clip 700 moves relative to the pump 750, the posts 719 travel through the channels 754.

In the locked position of the clip 700, the arms 714 extend about the cuff 620 and extend into the circumferential groove 632. The arms 714 have a substantially smooth inner surface 722 that engages the linking member 624 in the circumferential groove 632. The arms 714 also include teeth 716 (FIG. 26B) that fit between the ridges 636 to limit rotation of the cuff 620 relative to the clip 700. The teeth 716 can be disposed on the arms 714 and on a central extension 724 of the clip 700. Three teeth 716 are shown, positioned to press radially inward on the cuff 620 when the clip 700 is in its locked position. More teeth or fewer than three teeth can be used to promote rotational stability of the cuff 620.

The teeth 716 have an angled or chamfered edge 726 (FIG. 26D), permitting the teeth 716 to engage the cuff 620 when the cuff 620 is not fully seated against the circumferential flange 662. As the clip 700 moves into its locked position, the teeth 716 move radially inward toward the circumferential groove 632. The chamfered edge 726 engages the flanged portion 634 of the cuff 620, forcing the cuff 620 toward the upper surface 752 into a fully seated position against the circumferential groove 662.

The clip 700 includes substantially flat end portions 730 that are captured between the upper surface 752 and the cover 770. The cover 770 impedes the end portions 730 from moving away from the surface 752, and thus holds the posts 719 in the channels 754. Engagement of the end portions 730 between the upper surface 752 and the cover 770 also limits twisting along the arms 714 in response to axial loads exerted along the arms 714. The end portions 730, the teeth 716, and stabilizing posts 732 on the arms 714 can each have a height, H₂, along the longitudinal axis, Y, that is substantially the same as a corresponding height of the slot 740, thereby limiting travel of the clip 700 along the longitudinal axis and limiting tilting of the clip 700 within the slot 740.

The clip 700 includes a latch 733 that engages the cover 770 to limit retraction of the clip 700 from the locked position. The latch 733 includes a deflection beam 737 and an extension 738 located on a free end 739 of the deflection beam 737. The extension 738 extends from the top side 702 of the clip 700. The deflection beam 737 provides a resilient force that holds the extension 738 in a mating receptacle of, for example, the cover 770, unless overcome by a sufficient force.

The clip 700 includes ramp features 735 that extend from the bottom side 704. The ramp features 735 wedge the clip 700 between the cover 770 and the upper surface 752, stabilizing the clip 700 along the longitudinal axis, Y, of the cannula 650 when the clip 700 is in the locked position. By forcing the top side 702 toward the cover 770, the ramp features 735 also force engagement of the latch 733 to the mating receptacle.

The clip 700 includes visual indicators 736 on the bottom side 704 that indicate when the clip 700 is out of the locked position. The visual indicators 736 are, for example, recesses containing a colored material that is easily noticeable by a clinician. The visual indicators 736 are exposed, and thus visible from the bottom of the pump 750, when the clip 700 is not in the locked position. The visual indicators 736 are obscured when the clip 700 is in the locked position.

Referring to FIG. 27, the channels 754 in the surface 752 direct travel of the arms 714 as the clip 700 moves in the slot 740. As the clip 700 moves between an unlocked position to the locked position, the posts 719 move through the channels 754. The channels 754 have a width, W₂, that is larger than a diameter of the posts 719, which permits different lateral positions of the posts 719 in the channels 754. As described further below, the width, W₂, permits the posts 719 travel along different paths in the channels 754, rather than being constrained to travel along a single path.

The channels 754 are defined by inner walls 760 and outer walls 762. A lateral distance, D, between the inner walls 760 is greater than a distance between the posts 719 when the arms 714 are not flexed. As a result, positioning the posts 719 in the channels 754 flexes the arms 714 away from each other, causing the arms 714 to exert a resilient inward force against the inner walls 760. As the clip 700 travels in the slot 740, the posts 719 slide along the inner walls 760 unless displaced by, for example, the cuff 620.

The channels 754 define features that receive the posts 719. Each channel 754 defines, for example, a first end 764, a second end 765, and a detent 766, each of which can receive one of the posts 719. The posts 719 reside in the first ends 764 in an unlocked position of the clip 700, for example, when the clip 700 is fully retracted. At the first ends 764, the posts 719 engage the walls to impede the clip 700 from separating from the pump 750 by sliding out of the slot 740 along arrow A. The posts 719 reside in the second ends 765 when the clip 700 is in the locked position. The posts 719 reside in the detents 766 when the clip 700 is in a restrained position, for example, in which engagement of the posts 719 in the detents 766 impedes the clip 700 from travelling further toward the locked position. The unlocked position, the locked position, and the restrained position are stable positions of the clip 700 within the slot 740.

Referring to FIG. 28A, the clip 700 is retracted in the direction of arrow B₁, and each post 719 travels along a path 767 between the second end 765 and the first end 764. Various positions of the posts 719 are shown, but other features of the clip 700 are not shown. The pump 750 can be provided to a clinician with the clip 700 in the locked position, with the posts 719 residing in the second ends 765. In some implementations, the arms 714 are in a relaxed state in the locked position. The clinician retracts the clip 700 to permit the cannula 650 to be coupled to the cuff 620.

Referring to FIG. 28B, when the cuff 620 is not coupled about the cannula 650, advancing the clip 700 from the unlocked position toward the locked position places the clip 700 in the restrained position. As the clip 700 advances in the direction of arrow B₂, the arms 714 exert a lateral force inward toward the cannula 650, causing the posts 719 to travel in a path 768 along the inner walls 760. The posts 719 enter the detents 766 to impede the clip 700 from entering the locked position.

The clip 700 enters the restrained position when the cuff 620 is not properly coupled to the cannula 650, for example, when the cuff 620 is not located about the cannula 650 or the cuff 620 is improperly placed about the cannula 650. The placement of the clip 700 in the restrained discourages premature locking of the clip 700 and indicates to the clinician that the cuff 620 is not properly placed about the cannula 650. Patient safety is enhanced because the clip 700 does not enter the locked position if doing so would not actually secure the cuff 620 to the pump 750.

In some implementations, the clip 700 can enter the restrained position when only one of the posts 719 engages one of the detents 766. Either post 719 can independently impede the clip 700 from entering the locked position. In some instances, the cuff 620 may be seated only partially against the circumferential flange 662. For example, the cuff 620 may be placed in a tilted orientation such that the cuff 620 is not aligned in a plane perpendicular to the cannula 650. With the cuff 620 partially seated, one of the posts 719 may avoid the detent 766. Engagement of the other post 719 with its corresponding detent 766, however, will place the clip 700 in the restrained position rather than permitting the clip 700 to enter the locked position.

Referring to FIG. 28C, when the cuff 620 is properly coupled to the cannula 650, advancing the clip 700 in the direction of arrow B₂ moves the clip 700 into the locked position about the cuff 620. For clarity in illustration, the fastening member 622 and portions of the linking member 624 are not shown.

When the cuff 620 is coupled to the cannula 650, the flanged portions 634, 646 of the cuff 620 cover the detents 766. The cuff 620 blocks the posts 719 from entering the detents 766 and permits the posts 719 to enter the second ends 765. Between the unlocked position and the locked position, the posts 719 move along a path 769. The posts 719 slide along the outer circumference of the flanged portion 646, engaged to the cuff 620 by the resilient force of the arms 714, until the posts 719 reach the second ends 765. In the locked position, the arms 714 (not shown) extend into the circumferential groove 632, capturing the flanged portions 634, 646 between the arms 714 and the circumferential flange 662 of the cannula 650. The teeth 716 extend radially inward into the circumferential groove 632, becoming enmeshed between the ridges 636 to limit rotation of the cuff 620 relative to the cannula 650.

Referring to FIGS. 29A and 29B, when a clinician installs the pump 750, the visual indicators 736 on the clip 700 are exposed to the clinician's view. The visual indicators 736 indicate that the clip 700 is not securing the cuff 620, and thus that installation is incomplete. The visual indicators 736 are exposed in the unlocked position (FIG. 29A) and in the restrained position (FIG. 29B).

Referring to FIG. 29C, when the clip 700 enters the locked position, the pump 750 obscures the visual indicators 736, indicating to the clinician that the clip 700 has been properly locked about the cuff 620.

Referring to FIGS. 30A-30C, the cover 770 defines a mating receptacle 774, for example, a recess or an opening, that cooperates with the latch 733. The latch 733 does not secure the position of the clip 700 in the unlocked position (FIG. 30A) or the restrained position (FIG. 30B). In the locked position (FIG. 30C), the extension 738 extends into the mating receptacle 774 to impede retraction of the clip 700 in the direction of the arrow R.

Referring to FIG. 31, the extension 738 includes an angled leading edge 742 and an angled trailing edge 744 that engage the cover 770. The leading edge 742 engages an outer edge 746 of the cover 770 as the clip 700 travels into the locked position. The engagement of the leading edge 742 with the outer edge 746 deflects the deflection beam 737, permitting the extension 738 to slide under the outer edge 746 and into the mating receptacle 774. The trailing edge 744 engages an inner surface 748 of the mating receptacle 774 to limit removal of the clip 700.

The trailing edge 742 has a steeper slope than the leading edge 742. For example, the trailing edge 742 can have a slope of between approximately 70 degrees and approximately 85 degrees, and the leading edge can have a slope of between approximately 10 degrees to approximately 60 degrees. As a result, the amount of force required to dislodge the extension 738 from the mating receptacle 774 is greater than the force required to insert the extension into the mating receptacle 774. When removal of the clip 700 is desired, a clinician can engage a tool with the deflection beam 737 to move the extension 738 out of the mating receptacle 774, which permits the clip 700 to be retracted.

In some implementations, a plug can be fabricated for a cuff 20, 120, 320, 620. A plug can be placed in the opening 30, 130, 330, 630 of an implanted cuff 20, 120, 320, 620 after a pump 12, 250, 750 has been explanted. The plug can fill the opening 30, 130, 330, 630 to prevent blood from escaping through the cuff 20, 120, 320, 620 after the pump 12, 250, 750 is removed. Plugs can include features similar to those described for the cannulas 50, 150, 350, 650. As a result, a plug can be coupled to a corresponding cuff 20, 120, 320, 620 using one or more of the same mechanisms that couple a cuff 20, 120, 320, 620 to a cannula 50, 150, 350, 650. A plug can be further secured to a heart or to a cuff 20, 120, 320, 620 by sutures.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Implementations can include any appropriate combination or subcombination of features described above. For example, some of or all of the features described for the pumps 50, 250, 750, cuffs 20, 120, 320, 620, cannulas 50, 150, 350, 650, and clips 200, 700 can be combined or implemented individually. Accordingly, other implementations are within the scope of the following claims. 

What is claimed is:
 1. An implantable system comprising: a ventricular assist device (VAD) comprising an inlet cannula wherein the inlet cannula comprises a first circumferential taper; and a cuff for attachment to a heart and defining an opening for insertion of the inlet cannula into the opening, wherein the cuff comprises an annular fastening member and an attachment member, wherein the annular fastening member is configured to be sutured to heart tissue, wherein the attachment member comprises flexible extensions, wherein each of the flexible extensions comprises a lower tapered portion configured to interface with the first circumferential taper during insertion of the inlet cannula into the opening so as to cause the flexible extensions to flex outward to accommodate passing of the first circumferential taper along the opening, and wherein each of the flexible extensions is configured to interface with the inlet cannula to impede extraction of the inlet cannula from the opening.
 2. The implantable system of claim 1, wherein the flexible extensions and the first circumferential taper are configured to disengage during advancement of the inlet cannula along the opening to produce a reduction in resistance to advancement of the inlet cannula along the opening indicative of the inlet cannula being coupled to the cuff.
 3. The implantable system of claim 1, wherein: the inlet cannula comprises a second circumferential taper; and each of the flexible extensions comprises an upper tapered portion configured to interface with the second circumferential taper to impede extraction of the inlet cannula from the opening.
 4. The implantable system of claim 3, wherein tapers of the lower tapered portion and the first circumferential taper are less steep than tapers of the upper tapered portion and the second circumferential taper so that more force is required to decouple the inlet cannula from the cuff than to couple the inlet cannula with the cuff.
 5. The implantable system of claim 1, wherein the attachment member is formed of a metal.
 6. The implantable system of claim 1, wherein the attachment member comprises a ring portion having a wall with cutouts that partially define the flexible extensions.
 7. The implantable system of claim 6, wherein the attachment member comprises flanged portions that extend transverse to the wall.
 8. The implantable system of claim 7, wherein: the cuff comprises a linking member that couples the attachment member with the annular fastening member; and the linking member covers the flanged portions.
 9. The implantable system of claim 8, wherein: the inlet cannula comprises a second circumferential taper; and each of the flexible extensions comprises an upper tapered portion configured to interface with the second circumferential taper to press the linking member into engagement with a circumferential flange of the inlet cannula.
 10. The implantable system of claim 1, wherein the flexible extensions are disposed symmetrically around a circumference of the attachment member.
 11. An implantable system comprising: a ventricular assist device (VAD) comprising a cannula assembly, wherein the cannula assembly comprises an inlet cannula and a sealing ring disposed at least partially within an external circumferential groove of the inlet cannula; and a cuff for attachment to a heart and defining an opening for insertion of the cannula assembly into the opening, wherein the cuff comprises an annular fastening member and an attachment member, wherein the annular fastening member is configured to be sutured to heart tissue, wherein the attachment member comprises an inner circumferential groove configured to accommodate a portion of the sealing ring when the cannula assembly is in a coupled configuration with the cuff, and wherein engagement of the sealing ring with the attachment member and the cannula assembly in the coupled configuration inhibits extraction of the cannula assembly from the cuff.
 12. The implantable system of claim 11, wherein the attachment member comprises an inner circumferential taper that engages the sealing ring during insertion of the cannula assembly into the opening so as to compress the sealing ring prior to the sealing ring being partially received by the inner circumferential groove of the attachment member.
 13. The implantable system of claim 12, wherein expansion of the sealing ring into the external circumferential groove generates a tactile feedback indicative of the cannula assembly reaching the coupled configuration with the cuff.
 14. The implantable system of claim 12, wherein the sealing ring provides a hemostatic seal between the inlet cannula and the cuff.
 15. The implantable system of claim 11, wherein the cuff comprises a linking member that couples the attachment member with the annular fastening member.
 16. The implantable system of claim 15, wherein the inlet cannula comprises a circumferential flange configured to interface with the linking member to form a face seal when the cannula assembly is in the coupled configuration with the cuff.
 17. An implantable system comprising: a ventricular assist device (VAD) comprising an inlet cannula; and a cuff for attachment to a heart and defining an opening for insertion of the inlet cannula into the opening, wherein the cuff comprises an annular fastening member and an attachment member, wherein the annular fastening member is configured to be sutured to heart tissue, wherein the attachment member comprises flexible extensions, wherein each of the flexible extensions is configured to interface with the inlet cannula during insertion of the inlet cannula into the opening so as to cause the flexible extension to flex outward to accommodate passing of the inlet cannula along the opening, wherein each of the flexible extensions is configured to interface with the inlet cannula to impede extraction of the inlet cannula from the opening, wherein the cuff comprises a linking member that couples the attachment member with the annular fastening member, wherein the linking member is formed of an elastomer, and wherein the inlet cannula comprises a circumferential flange configured to interface with the linking member to form a face seal when the inlet cannula is in a fully inserted configuration within the opening.
 18. The implantable system of claim 17, wherein: the inlet cannula comprises a first circumferential taper; and each of the flexible extensions comprises a lower tapered portion configured to interface with the first circumferential taper during insertion of the inlet cannula into the opening so as to cause the flexible extensions to flex outward to accommodate passing of the first circumferential taper along the opening.
 19. An implantable system comprising: a ventricular assist device (VAD) comprising an inlet cannula; and a cuff for attachment to a heart and defining an opening for insertion of the inlet cannula into the opening, wherein the cuff comprises an annular fastening member and an attachment member, wherein the annular fastening member is configured to be sutured to heart tissue, wherein the attachment member comprises flexible extensions, wherein each of the flexible extensions is configured to interface with the inlet cannula during insertion of the inlet cannula into the opening so as to cause the flexible extension to flex outward to accommodate passing of the inlet cannula along the opening, wherein each of the flexible extensions is configured to interface with the inlet cannula to impede extraction of the inlet cannula from the opening, wherein the attachment member comprises a ring portion having a wall with cutouts that partially define the flexible extensions, wherein the attachment member comprises flanged portions that extend transverse to the wall, wherein the cuff comprises a linking member that couples the attachment member with the annular fastening member, and wherein the linking member covers the flanged portions.
 20. The implantable system of claim 19, wherein: the inlet cannula comprises an inlet cannula circumferential taper; and each of the flexible extensions comprises an upper tapered portion configured to interface with the inlet cannula circumferential taper to press the linking member into engagement with a circumferential flange of the inlet cannula. 